Project Summary/Abstract Lung cancer (LCa) is the second most common malignancy in the US with about 222,500 new cases and 155,900 deaths each year. HIV-infected individuals and AIDS patients have increased relative risk of LCa by 250% after controlling for other potential risk factors. LCa in HIV+ people under antiretroviral therapy (ART) is diagnosed at younger ages than those in the general population. This trend in the ART era is implicitly attributed to prolonged life span and aging of the population. The success of new approaches to control lung tumorigenesis in the population is contingent to identify HIV-specific mechanisms that facilitate the tumor progression and metastasis. HIV-infected T cells release a variety of immunologically active exosomes, small vesicles of endocytic origin, to influence intercellular communication and material transfer at both local and distant sites, thus potentially contribute to enhanced risk for tumorigenesis. Our preliminary studies have found that exosomes secreted by HIV-infected T cells and purified from the blood of lung cancer patients of people living with HIV (PLWH) significantly stimulated lung cancer cell proliferation. HIV-associated exosomes induced MAP kinase ERK1/2 activation via interaction with epidermal growth factor receptor (EGFR) and the toll like receptor 3 (TLR3). Mechanistically, the HIV trans-activation response (TAR) element RNA, which exists in excess of other HIV RNAs in exosome from HIV-infected T cells, is responsible for enhanced cancer cell proliferation and proto-oncogene expression. We have established a bone marrow transplant (BMT) mouse model in which lethally-irradiated FVB mice were grafted with syngeneic bone marrow cells of Tg26 HIV- transgenic mice. Growth and metastasis of allografts LCa cells were significantly enhanced in grafted mice containing HIV+ bone marrow cells compared with that in non-grafted control mice. However, reconstitution of circulating immune cells and bone marrow remained the same between two groups of mice, suggesting that TAR RNA-bearing exosomes from reconstituted HIV+ immune cells may promote LCa progression in the BMT model. Taken together, these data lead us to hypothesize that TAR RNA-bearing exosomes from HIV-infected immune cells promote lung cancer growth and progression and that controlling release of the exosomes or directly targeting the TAR RNA may serve as an adjuvant for prevention and treatment of lung cancer in HIV- infected individuals. To test this hypothesis, we will first delineate the mechanism by which HIV-1-infected T- cell exosomes stimulate LCa growth and progression in vivo using the BMT model. The potentials for therapeutic intervention of LCa promotion by HIV will be examined through inhibition of exosome production and neutralization of TAR RNA. Finally, we will comprehensively examine the HIV-positive exosomal membrane proteins for interaction with EGFR and HIV-specific cargo components in the circulation using our novel EV-omics approach. Completion of the proposed studies will shed light on the mechanisms underlying HIV-mediated promotion of LCa and lay a foundation for therapeutic intervention of non-AIDS-defining cancers.